The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
In the past, the electronics industry utilized various methods and structures to form switching power supply controllers that regulated an output voltage to a desired value. In some cases, the power supply systems included a transformer and used a power switch to control current through a primary side of the transformer and a secondary switch in the secondary side of the transformer. Often, a signal from the secondary side of the transformer was used as a control signal to control the switching of the secondary switch. One example of such a power supply system is disclosed in U.S. Pat. No. 6,535,400 that issued to Christopher David Bridge on Mar. 18, 2003. One problem with such power supply systems was noise that was created on the synchronization signal due to the switching of currents through the secondary side of the transformer. These noise signals often resulted in inefficient operation of the power supply system.
Also, the number of package terminals used for an integrated circuit had an effect on the cost of the integrated circuit. The more terminals, the more complex the package, thus, the higher the cost. When integrating a secondary side power supply controller, it was important to minimize the number of pins utilized for the power supply control.
Accordingly, it is desirable to have a circuit that minimizes the effect of oscillations of the synchronization signal and that reduces the number of terminals required for the circuit.
For simplicity and clarity of the illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention. It will be appreciated by those skilled in the art that the words during, while, and when as used herein are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as a propagation delay, between the reaction that is initiated by the initial action.